5. Discussion
The major findings of this study were as follows: 1) LBB capture
threshold and pacing impedance were stable in the LBBAP population; 2)
after LBBAP, QRS duration was significantly decreased; 3) learning
curves for LBBAP procedures continued to improve with increasing
operator experience; and 4) higher success rates and lower complication
rates were achieved as experience increased.
Although HBP, which was first introduced by Deshmukh et al. in
2000,14 has been suggested as the ideal approach for
physiological ventricular activation,15 wider clinical
application of HBP is limited by several problems, including technical
difficulties in identifying the precise location, variable success
rates, and potential risk of premature battery depletion and lead
revisions due to progressive increases in capture
thresholds.15, 16
In this regard, LBBAP, which has a stable and lower capture threshold
and a similarly paced QRS duration to HBP, has emerged as a new
physiological conduction system modality.4, 5, 17LBBAP presents a simpler implant technique, shorter fluoroscopy, and
shorter procedure time with a steeper learning curve compared to HBP;
thus, LBBAP is now widely used as an alternative for conventional SP and
considered as the first strategy for patients in whom a high burden of
ventricular pacing is anticipated.5, 17 However, LBBAP
has not yet reached widespread clinical use, and the main obstacle to
widespread use is the limited array of available tools for LBBAP
implantation. Although most cases of LBBAP have been exclusively
performed using LLL with a fixed helix design and a pre-shaped sheath
dedicated to this lead, LLL is not available to all manufacturers and
implanters; thus there is a limited ability to offer LBBAP to all
patients. Therefore, the ability to perform LBBAP with SDLs seems to
encourage more implanters to attempt the LBBAP.
In this study, the plateau phase of the procedure time for LBBAP with
SDL began from the 24th case, which is shorter than the previously
reported learning curves ( 30–50 cases) of HBP and even LBBAP using
LLL.18-20 In addition to the known advantages of the
shorter learning curve of LBBAP compared to those of HBP, familiarity
with SDL also contributed to a shorter learning curve than that of HBP.
These data are encouraging for centers considering the implementation of
an LBBAP procedure, suggesting improved procedural results and
procedural time with increased operator experience, which may lead to a
more challenging procedure.